<s>
Cheney	B-General_Concept
's	I-General_Concept
algorithm	I-General_Concept
,	O
first	O
described	O
in	O
a	O
1970	O
ACM	O
paper	O
by	O
C.J.	O
</s>
<s>
Cheney	O
,	O
is	O
a	O
stop	O
and	O
copy	O
method	O
of	O
tracing	B-General_Concept
garbage	I-General_Concept
collection	I-General_Concept
in	O
computer	O
software	O
systems	O
.	O
</s>
<s>
Cheney	B-General_Concept
's	I-General_Concept
algorithm	I-General_Concept
reclaims	O
items	O
as	O
follows	O
:	O
</s>
<s>
Cheney	B-General_Concept
's	I-General_Concept
algorithm	I-General_Concept
is	O
an	O
example	O
of	O
a	O
tri-color	O
marking	O
garbage	O
collector	O
.	O
</s>
